1. Field of the Invention
The present invention relates to a display device, an electronic appliance, an optical member, a display panel, a controller, and a control method and a control program for driving the display panel.
2. Description of the Related Art
Due to rapid developments in display devices, those display devices are loaded on various terminal devices in large and small sizes and used in various scenes.
When displaying important information such as privacy information that needs to be kept confidential, it is necessary to have a confidentiality keeping function so that such information cannot be exposed to the eyes of third parties. Therefore, there has been investigated to develop a peeping prevention technique that is capable of concealing the displayed information.
As related techniques of such display device, there are those disclosed in Japanese Unexamined Patent Publication 6-110403 (Patent Document 1) and Japanese Unexamined Patent Document 2003-233074 (Patent Document 2) described below, for example.
Patent Document 1 discloses a structure in which a visualizing device is placed between a specific user and a display panel.
The visualizing device is an optical shutter which selectively transmits only a specific image that is required by the specific user from a plurality of images that are displayed sequentially on the display panel.
This makes it possible only for the specific user who has the visualizing device to visually recognize confidential information.
Other surrounding unspecified people having no visualizing device are to visually recognize a plurality of sequentially displayed images in a mixed manner, so that those unspecified people cannot recognize the confidential information. With this, a confidentiality keeping function can be achieved.
Further, regarding a liquid crystal display device depicted in Patent Document 2, disclosed is a structure in which area with a different alignment condition of liquid crystal molecules is formed larger than a pixel. In the area larger than the pixel, different viewing angle properties can be achieved due to the difference in the alignment conditions.
Thus, the alignment condition and the driving condition are so set that the patterns of the area with different alignment condition are visually recognized when the display device is viewed from directions other than the front-face direction.
This makes it possible to display the fixed patterns in a superimposed manner for oblique directions, so that displayed information can be prevented from being visually recognized from those directions.
In the meantime, almost no pattern of the area with different alignment condition is visually recognized when the display device is viewed from the front-face direction, so that the displayed information can be visually recognized from that direction.
Furthermore, with the liquid crystal display device disclosed in Patent Document 2, the confidentiality keeping function is achieved by utilizing the angles of viewing the display device. Therefore, it is unnecessary to wear special optical shutter eye glasses, so that a troublesome work for the users can be lightened.
However, there are following shortcomings in the display devices of the related techniques.
That is, with the display device depicted in Patent Document 1, there is such a shortcoming that it requires a troublesome work of wearing special optical shutter eyeglasses as mentioned above.
Further, with the liquid crystal display device depicted in Patent Document 2, there may be cases where third parties can grasp displayed contents because the patterns that can be superimposed on the displayed image are coarser than the pixels and fixed, even though no troublesome work of wearing special eyeglasses is required.
Furthermore, there is also such a shortcoming that a normal display cannot be done, since the fixed patterns are always superimposed on the display images for the directions other than the front-face direction.